The present invention relates to surgical electrodes in general, and more particularly to improvements in surgical electrodes which can be implanted into the thorax of a patient to connect the heart with an external cardiac pacing or monitoring instrument. One end of a cardiac electrode is implanted into a patient's heart (e.g., in a manner as disclosed in the commonly owned copending patent applications Ser. Nos. 719,901 and 740,013 respectively filed Apr. 4 and May 31, 1985) and the other end (terminal portion) of the electrode extends from the thorax to be connected, or to be connectable, with an external pacemaker, an electrocardiograph or another medical instrument.
U.S. Pat. No. 4,010,756 discloses a heart pacer lead wire with a break-away needle. When the needle is broken away, the thus obtained plug must be connected with a cardiac pacer or with a cardiac monitoring instrument. As a rule, the instruments which are to be connected to a cardiac electrode have electrode clamping means or they utilize chucks which can receive and hold the exposed ends of the terminal portions of lead wires. The chucks are designed to receive plugs having a diameter in the range of two millimeters. Such plugs must be secured to the terminal portions of lead wires in a time-consuming manner. Known proposals include the utilization of specially designed clamps which serve as adapters between a plug and the terminal portion of the lead wire. Furthermore, it is still quite customary to utilize such relatively unreliable expedients as adhesive-coated tapes or bands in order to ensure that the terminal portion which extends from the thorax of a patient can be attached to the corresponding terminal of a medical instrument.
German Pat. No. 10 36 969 discloses a plug which can be used in laboratories and repair shops for electrical devices to establish a temporary connection between normally separated parts. The plug is rather bulky so that it cannot be used to connect the terminal portion of a lead wire with a cardiac pacing or monitoring instrument. There are additional reasons why such plug cannot be used in connection with cardiac electrodes even if its dimensions were reduced to the required size. Thus, the plug employs a male component having a transverse hole and a sleeve which is formed with two registering holes movable into register with the transverse hole for insertion of a wire through the sleeve and the male component. That portion of the wire which is caused to pass through the registering holes must be free of insulation in order to establish satisfactory electrical contact with the male component. The sleeve is then shifted axially to bend those portions of the wire which are immediately adjacent to the transverse hole. Blank portions of the wire are accessible at the exterior of the sleeve after the latter is moved to the operative position so that, were such plug used to connect the terminal portion of a lead wire with a medical instrument, the noninsulated portions of the wire would be likely to come into contact with the hands of nurses or other attendants to transmit undesirable electrical charges wire with attendant irregularity of heartbeat and danger to the life of the patient. An additional drawback of the patented plug is that it comprises a substantial number of parts including a spring which serves to bias the sleeve to a predetermined position.
U.S. Pat. No. 4,017,756 and German Offenlegungsschrift No. 28 46 136 disclose cardiac electrodes which employ needles and are provided with means for facilitating separation of the needles from the terminal portions of the lead wires so that the thus obtained plugs can be inserted into sockets. A drawback of such proposal is that the plug is extremely thin so that it does not fit into standard sockets. Furthermore, it is difficult to connect such plugs to extension cords or other types of adapters.
U.S. Pat. No. 4,442,840 discloses an electrical connector apparatus which employs a rather complex coupling consisting of synthetic plastic material. The construction of the coupling is such that the electrical connection between the terminal portion of the lead wire and the plug cannot be inspected except by taking the coupling apart. Furthermore, it is necessary to employ an extension cable which connects the terminal portion to the socket of a medical instrument.